The authors report the clinical and polygraphic features of rhythmic teeth grinding observed in a patient as the predominant symptom related to temporal lobe seizures during sleep and wakefulness. This observation demonstrates that exceptionally a teeth-grinding event can be not only a parasomnia (sleep bruxism) but also an epileptic-related motor event. Electromyographic and autonomic features of seizure-related teeth grinding support the interpretation of this motor phenomenon as a particular form of masticatory activity.